This invention relates to the utilization of chemical wastes and residues having a high content of calcined aluminum oxides by subjecting them to a hydrothermal reaction with sodium hydroxide at a temperature above about 180.degree. C. to form sodium aluminate solution, wherein the sodium aluminate solution thus formed can be used for further reactions.
Calcined aluminum oxides are used for a variety of commercial applications, for example as drying agents and sorbents, catalysts and catalyst supports, or as filter aids. "Spent" products of this type, i.e. contaminated products of which the sorptive or catalytic effect has been exhausted or which can no longer be used for other reasons, generally have to be dumped. Depending on the nature of the charge or contamination, they may even have to be subjected to a pretreatment or stored in special dumps.
Accordingly, a process is needed for the ecologically and economically efficient utilization of chemical wastes and residues containing calcined aluminum oxides, in which the disadvantages referred to above are avoided. In addition, the process should achieve as high a volume/time yield as possible for as low a consumption of energy as possible.
It is known to the expert that the high-temperature modifications of aluminum oxide are chemically very resistant. It is expressly pointed out in the literature that .alpha.-Al.sub.2 O.sub.3 in particular is "substantially insoluble in alkalis" (GMELIN).